Aqueous separation liquid and process for removing paint overspray from a paint spray booth

Abstract

The present invention relates to an aqueous separation liquid comprising at least 49.9 wt. % water, 5 to 50 wt. % of at least one organic water-soluble polyol, based on the total weight of the aqueous separation liquid, and at least one low molecular weight cellulose derivative as rheology modifier, and to the use of this liquid in a process for removing paint overspray from a paint spray booth.

The invention claimed is: 
     
       1. An aqueous separation liquid for capturing paint overspray from a gas stream comprising:
 a) at least 49.9 weight percent water, based on the total weight of the aqueous separation liquid, 
 b) 5 to 50 weight percent of at least one organic water-soluble polyol, based on the total weight of the aqueous separation liquid, and 
 c) at least one cellulose derivative having a viscosity of less than 200 mPa·s as measured with a Visco Tester VT5 using a R2 spindle at a velocity of rotation of 60 rpm and a temperature of 20° C. for a 1 weight percent solution of the cellulose derivative in water, based on the total weight of the solution, 
 wherein components b) and c) are different from each other, and 
 the aqueous separation liquid has a viscosity in terms of outflow time in the range from 11 s to 50 s, as measured according to ISO 2431:2011 using a 4 mm flow cup at 20° C. 
 
     
     
       2. The aqueous separation liquid of  claim 1 , wherein the at least one cellulose derivative has a viscosity of less than 100 mPa·s as measured with a Visco Tester VT5 using a R2 spindle at a velocity of rotation of 60 rpm and a temperature of 20° C. for a 1 weight percent solution of the cellulose derivative in water, based on the total weight of the solution. 
     
     
       3. The aqueous separation liquid  claim 1 , wherein the at least one cellulose derivative comprises a cellulose ether having a molar degree of substitution in the range from 2.0 to 2.5. 
     
     
       4. The aqueous separation liquid of  claim 3 , wherein the cellulose ether comprises hydroxyethyl cellulose. 
     
     
       5. The aqueous separation liquid of  claim 4 , wherein the hydroxyethyl cellulose has a molar degree of substitution of from 2.0 to 2. 
     
     
       6. The aqueous separation liquid of  claim 1 , wherein the at least one organic water-soluble polyol comprises a monomeric polyol or a polymeric polyol. 
     
     
       7. The aqueous separation liquid of  claim 6 , wherein the monomeric polyol comprises a monomeric polyol having at least three hydroxyl groups per molecule. 
     
     
       8. The aqueous separation liquid of  claim 6 , wherein the monomeric polyol comprises ethylene glycol, propylene glycol, glycerol, pentaerythritol, or combinations thereof. 
     
     
       9. The aqueous separation of  claim 6 , wherein the polymeric polyol comprises polymeric polyols having a number average molecular weight of 200 to 3,000, as measured by gel permeation chromatography using polystyrene calibration standards. 
     
     
       10. The aqueous separation according to  claim 6 , wherein the polymeric polyol comprises poly(ethylene glycols), poly(propylene glycols), mixed poly((ethylene)(propylene) glycols), polyester polyols, acrylic polyols, polyurethane polyols, or combinations thereof. 
     
     
       11. The aqueous separation liquid of  claim 1 , wherein the aqueous separation liquid has a viscosity in terms of outflow time of 11 s to 50 s, as measured according to ISO 2431:2011 using a 4 mm flow cup at 20° C. 
     
     
       12. The aqueous separation liquid of  claim 1 , comprising the at least one organic water-soluble polyol in an amount of 7 weight percent to 40 weight percent, based on the total weight of the aqueous separation liquid, and the at least one cellulose derivative in an amount of 0.1 weight percent to 10 weight percent, based on the total weight of the aqueous separation liquid. 
     
     
       13. The aqueous separation liquid of  claim 1 , further comprising at least one surfactant. 
     
     
       14. The aqueous separation liquid of  claim 13 , wherein the surfactant comprises at least one non-ionic surfactant comprising poly(alkylene glycol) fatty alcohol ethers, alkylphenol poly(alkylene glycol) ethers, poly(alkylene glycol) fatty acid esters, fatty acid mono glycerides, poly(alkylene glycol) mono fatty acid esters, fatty acid mono alkanol amides, fatty acid dialkanol amides, alkoxylated fatty acid mono alkanol amides, alkoxylated fatty acid dialkanol amides, fatty acid partial esters of pentaerythritol, alkoxylated fatty acid partial esters of pentaerythritol, sorbitan fatty acid esters, alkoxylated sorbitan fatty acid esters, acetylenic dials, alkoxylated acetylenic dials, alkyl amino oxides, alkoxylated alkyl amino oxides, fluoro containing tensides, 6 polysiloxane based tensides, or combinations thereof. 
     
     
       15. The aqueous separation liquid of  claim 1 , further comprising at least one paint detackifying agent comprising polyamines, polyamide amines, polyquarternary amine polymers, alumosilicates, silicates, aluminum compounds, polycarboxylates, or combinations thereof. 
     
     
       16. The aqueous separation liquid of  claim 1 , further comprising at least one additive comprising preservative agents, biocides, pH-regulators, defoamers, or combinations thereof. 
     
     
       17. A process for removing paint overspray from a paint spray booth comprising:
 i) directing a gas stream through a paint spray booth; 
 ii) contacting paint overspray with the gas stream flowing through the paint spray booth thereby forming an overspray-laden gas stream containing paint particles and/or droplets dispersed therein, 
 iii) forming a flowing substantially continuous liquid film of the aqueous separation liquid of  claim 1  on at least one surface that defines at least a part of the flow path of the overspray-laden gas stream; 
 iv) contacting the overspray-laden gas stream with said liquid film, thereby transferring paint particles and/or droplets from the overspray-laden gas stream into the separation liquid to form a paint loaded separation liquid; and 
 v) removing the paint loaded separation liquid and the gas stream having a reduced overspray load. 
 
     
     
       18. The process of  claim 17 , wherein the contacting in step iv) comprises directing the overspray-laden gas stream through an electrostatic scrubber, wherein particles and/or droplets dispersed in the gas stream are ionized and then directed by an electric field to the flowing substantially continuous liquid film of the aqueous separation liquid thereby transferring paint particles and/or droplets from the overspray-laden gas stream into the separation liquid to form the paint loaded separation liquid. 
     
     
       19. The process of  claim 17 , further comprising:
 vi) at least partially separating the paint components from the removed paint loaded separation liquid to obtain a purified separation liquid, and/or 
 vii) conditioning and/or further purifying the removed gas stream to obtain a processed gas stream; and optionally 
 viii) at least partially recycling the purified separation liquid to step iii) and/or at least partially recycling the processed gas stream to step i). 
 
     
     
       20. A method for painting a substrate comprising:
 spraying a paint onto a substrate in a paint spraying booth, thereby 
 obtaining a painted substrate and paint overspray; and 
 removing the paint overspray with the process of  claim 17 .